During the past year, we have used NCS-A data to investigate the lifetime prevalence of mental disorder and mental health service use among adolescents by immigrant generation and racial/ethnic minority status, and found that some groups of adolescents are at greater risk for mental disorder than third and greater generation non-Hispanic white adolescents, while other groups are at lower risk. Importantly, mental health service use was less common among immigrant and minority adolescents controlling for disorder presence, indicating a disparity in treatment availability or utilization (Georgiades et al, 2018). We also examined the influence of adolescent-rated parenting style on the prevalence of mental disorders and found that high ratings of parental care were associated with reduced risk of a number of mental disorders, while high ratings of parental control were associated with increased risk (Eun et al, 2017). We also assessed associations between engagement in regular physical activity and adolescent mental disorder (He et al, in press). Findings indicated that physical activity was associated with lower odds of mood disorder and psychological distress, but higher odds of alcohol use disorder and eating disorder. The NCS-A is the sole source of U.S. national estimates of the prevalence of a comprehensive array of mental disorders in adolescents, which is why it continues to be a valuable scientific resource despite the fact that it was conducted over 10 years ago. Recent claims in the media of a dramatic increase in the prevalence of mental health problems among U.S. youth prompted us to publish an editorial clarifying that there is, in fact, little evidence to back such claims (Merikangas 2018). Complicating this issue is the lack of recent national U.S. data that would allow for a reliable comparison of rates. There is a clear need for the collection of such information for service planning as well as for research into biologic, genetic, and environmental influences on the occurrence of mental disorders in youth. Longitudinal studies have the potential to shed light not only on causes of disorder, but on the underlying nature of mental health and illness. In collaboration with our colleagues in Zurich, we used data from the 30-year Zurich Cohort Study to demonstrate the existence of a subthreshold mania syndrome among about one-fifth of members of the general population who have MDD (Angst et al, 2018). Those with the mania syndrome were more similar to those with clinical Bipolar Disorder (BPD) in terms of family history of mania, onset and course of illness, cyclothymic temperament, and comorbidity, than they were to those with pure MDD. Because the presence of subthreshold mania may increase risk for future manic disorder, early identification of those with subthreshold mania syndromes could help prevent progression to severe disorder. In addition to complications stemming from the underlying dimensionality of mania and depression, treatment and research in BPD is hindered by ethnic and cultural homogeneity among research participants and racial disparities in treatment access and provision. Therefore, with colleagues at the Mayo Clinic, we undertook a descriptive review of the literature to understand racial differences and diagnostic disparities in BPD, comparing African Americans to those of European ancestry (Akinhanmi et al, 2018). A number of studies have reported clinical misdiagnosis of black patients as well as differences in treatment quality, with implications for the disparity in illness course and burden. In addition, genetic studies of BPD often exclude participants not of European descent, which limits the impact of genetic discoveries. We concluded that increased effort is needed by the research community to understand the origins of such disparities and to increase representation of non-European populations in genetic and psychiatric research. In our collaboration with researchers from the CoLaus/PsyCoLaus study in Switzerland, we evaluated the longitudinal and bidirectional association between mood disorders and levels of inflammatory markers and found that the atypical subtype of depression at baseline was associated with increased levels of high-sensitivity C-reactive protein at follow-up, whereas inflammation at baseline was not a risk factor for subsequent mood disorders (Glaus et al, 2017). Similarly, we analyzed the association between anxiety disorders and inflammation and we found that anxiety disorders at baseline (in particular agoraphobia) were associated with a steeper increase of hsCRP levels over the follow-up period. Moreover, there was no evidence for chronic low-grade inflammation as a predictor of future anxiety disorders (Glaus et al, 2017). These findings suggest that inflammation may be a consequence, but not a predictor of mental disorders. A current issue in mental health research is the need for transdiagnostic approaches to studying mental illness and brain development. Toward this end, we have been active in the development and establishment of the Child Mind Institute's Healthy Brain Network (HBN) study and have recently published a description of the HBN project goals, plan, and protocols (Alexander et al, 2017). The HBN will serve as a resource for researchers in the field who wish to tackle transdiagnostic research questions related to mental health in children and youth. Public Health Impact: The NCS-A study was the first with comprehensive domains of emotional and behavior disorders in a nationally representative sample of U.S. youth, and the results have had significant public health impact. The investigation of risk factors during development, which the NCS-A makes possible, is extremely important in mental health because many cases of mental disorder first arise during or prior to young adulthood and because brain development is implicated in the etiology of many mental disorders. The Zurich Cohort Study is an extremely valuable data source, as it is the longest community-based longitudinal study in which participants were enrolled at the beginning of adulthood. The detailed phenomenology collected as part of that study enables us to conduct research that informs our understanding of the nature of mental disorders, which may ultimately impact psychiatric treatment and research. Our work on the CoLaus/PsyCoLaus study has substantial potential for public health impact because it combines information regarding cardiovascular risk factors and mental disorders in a longitudinal study. Our recent work represents only the beginning of a research program that we hope will help to tease apart the longitudinal relationships between physical and mental health in the population. Future Plans: We are currently focusing on mental disorders and other health related outcomes in relation to: 1) physical illnesses, 2) environmental exposures such as noise and light, 3) residential and school mobility, 4) peer and family social network characteristics, 5) lifestyle factors such as physical activity and sleep, 6) neighborhood and school-level exposures, and 7) biomarkers and health risk factors. Importantly, in the next year we plan to begin establishing a database of existing studies in child and adolescent psychiatric epidemiology to facilitate collaborations across the discipline. This will serve as a resource for the entire field and encourage continued use of these valuable existing data sources in order to maximize their scientific utility. Similarly, we plan to continue working with investigators of the HBN to plan completion of the study and dissemination of data to the scientific community. We also plan to analyze this data in-house to address questions regarding the role of child and adolescent development in the etiology of mental disorder.